Abstract: Current evidence suggests that Mexican-American adolescents living on the U.S.-Mexico border experience higher rates of substance use-related problems compared to non-border Mexican-Americans and their non- Hispanic white counterparts. Because environmental factors are central to the experimentation with and initiation of substance use among adolescents , the unique environmental context of the U.S. Mexico border might exacerbate the risk of substance use for adolescents residing there. However, despite the socioeconomic and environmental risk factors that should increase substance use among these adolescents, the sociocultural characteristics of the border region might be protective against substance use among adolescents. The examination of environmental factors that increase the risk of, or protect against, substance use among border adolescents, as well as their patterns of substance use, is unprecedented, leaving a critical gap in the literature on adolescent substance use at the U.S.-Mexico border. This lack of data, coupled with the evidence to suggest that the border region is exceptionally unique due to its socioeconomic and sociocultural characteristics, warrants the need for substance use research that engages the adolescents that exist and interact in this environment. Ms. Valdez has extensive training in health behavior and adolescent substance use, and has lived experience within/of the unique context of the border region, which makes her well-versed in the study of sociocultural and socioeconomic risk factors and how they relate to specific risk behavior among adolescents. However, she requires additional training to extend her instrument design and testing skills, and her advanced quantitative analysis skills. This predoctoral fellowship will help Ms. Valdez to (1) develop/adapt a culturally- and regionally-responsive survey, (2) assess the reliability and validity of the measure, and (3) refine her quantitative data collection and analysis skills. With mentorship from Dr. Scott Carvajal and a panel of experts, Ms. Valdez and a local youth health coalition will engage in a Youth Participatory Action Research (YPAR) project in the border community of Douglas, AZ, to develop a mixed methods study to examine the environmental factors that influence substance use among border adolescents. Using YPAR methods, the research team will use the Photovoice process to examine the perceived environmental factors that increase risk of, or protect against, substance use among adolescents living at the border. Themes that are elicited and identified from the Photovoice Process will inform the development and delivery of the Border Adolescent Substance Use Survey (BASUS) to assess environmental factors that influence patterns of adolescent substance use at the border. This research is critical to our understanding of adolescent substance use at the U.S.-Mexico border and its rich, YPAR-informed data will help advance the field of prevention. The training plan and research strategy in this application will give Ms. Valdez the time, resources, and mentorship that she needs to succeed as an independent researcher and allow her to make significant contributions to the field.